Duxelles: Chop the mushrooms very, very finely. This can be done in a food processor if you have one.

Empty all the chopped mushrooms into a deep, heavy bottomed frying pan. Add the stock, sherry, Teriyaki sauce, spring onions and tarragon. Stir it all up. The mushrooms will be barely moistened but it doesn't matter.

Cook over a moderate heat, stirring occasionally until the mushrooms have rendered quite a bit of liquid. Turn the heat up a bit and simmer briskly, stirring occasionally until the mushrooms are very dark, very thick and quite dry. Reduce the heat as the liquid cooks away, to minimise scorching. Season to taste. Store in the fridge until needed.

Mushrooms: Preheat the oven to 200 °C/400F/gas 6. Cut the stems off the mushrooms (don't throw them away, chop them and saute in stock, sherry and soy sauce, or use in duxelles).

With a teaspoon hollow out the mushrooms a bit so that they will hold the stuffing nicely. Salt and pepper them lightly.

Fill each mushroom with your chosen filling, mounding it nicely.If you can wish you can sprinkle some Parmesan on top. Tear off a piece of baking parchment that will generously enfold 2 of the stuffed mushrooms. Fold the paper in half and crease it to the fold. Open and mist the paper lightly and evenly with oil spray. Place 2 mushrooms, evenly spaced, stuffing side up on the bottom half of the parchment. Fold over and seal securely. The parcel should be roomy, but well sealed. Repeat for the remaining mushrooms. Slide the parcels onto a baking tray bring to the oven and slide off the tray, directly onto the oven shelf. Bake for 25-35 minutes. The parcels will darken and puff up and the aroma will be wonderful.

When done, slide the parcels back onto the baking tray and bring to the table. With scissors, cut a cross on the top of each packet. Carefully, with a broad spatula, lift the stuffed mushrooms onto a platter. Serve at once.